6 Elementary Manual of Zoology. 
and paralysing prey. Reproduction takes place in two ways. Oue of 
these is by the formation of out-growths or buds, which develop into 
animals like the parent and drop off, The other is by the production 
of two different kinds of minute cells, known as Ova and Spermatozoa 
respectively. These specialised cells are merely out-growths of the cells 
of the body wall. The spermatozoan cellis free swimming, It joins up 
with an ovum cell, which afterwards drops off and develops into a Hydra 
like the parent. 
B.—CCELOMATA. 
. (1)—EcHINOoDERMATA. 
The Echinodermata are a group of animals which are eutirely’ con- 
fined to the sea. They are therefore of little importance from an Indian 
Forester’s point of view, and the only reason for noticing them is on 
account of their being so well known and distinct. Like other 
Ceelomata, they are furnished with a body cavity around the digestive 
tract, When full grown they are radially symmetrical, their “boilies 
being usually arranged pentagonally and supported by calcareous 
armour. They have a more or less developed system of nerves around 
the mouth, also blood-vessels, and a very characteristic system of vessels 
containing water (water vascular system), which subserves locomotion. 
The chief groups are the star-fishes (Asteroidea) , the sea-urchins (Echinoi- 
dea), sea-lilies (Crinoidea), and the sea-cucumbers (Holothuroidea). 
The students should examine the fossil Echinoderms in the School 
Museum, and make out such features of external anatomy as the mouth, 
anus and radiate arrangement of the body, but no detailed acquaintance 
with the group will be required. 
(2) —VERMES. (WORMS). 
This is an ill-defined group of Celomate animals. It comprises 
a Jarge number of very distinct creatures which differ from each other 
so widely that some zoologists prefer to class the different groups 
altogether separately from each other. The most characteristic features 
which tbe various representatives have in common are their elongated 
shape, their bilateral symmetry and their paired excretory canals. Even 
these very general characteristics, however, are so subject to exception, 
that perhaps the best way to characterise the group is to compare it with 
the other large sections of the Cclomata and show how the Vermes 
differ in each case. Thus from the Echinodermata they differ in bemg 
bilaterally symmetrical throughout life; from the Mollusca they differ 
in not possessing the characteristic ventral foot of that group; from 
the Arthropoda they differ in not possessing jointed armour-clad append- 
ages ; while from the Chordata they differ in not possessing a notochord. 
